This invention relates in general to quadrature amplitude modulation (QAM) receivers and more particularly to a fading resistant quadrature amplitude modulation receiver.
In products such as a wireless device or the like, many different schemes exist to convey information from a transmitter to its receiver. Conventional voice communication systems such as the IS-95 based CDMA system use digital modulation schemes such as Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK) to convey voice information to the wireless device. Market conditions and advances in technology have pressed designers of wireless devices to use more exotic information delivery schemes such as multi-level QAM in an attempt to increase the information carrying capacity or spectral efficiency of a wireless communication system. These changes, however, and not without their problems. Higher order modulation schemes such as 8 PSK or 16, 32 and 64 QAM are particularly susceptible to conditions such as Rayleigh fading, a phenomena that creates widely varying signal strength conditions at the receiver. As such the Eb/NO requirement at the receiver to decode a multi-level QAM signal is much higher than the Eb/No requirement to decode a BPSK/QPSK signal.
Thus, what is needed is a system and method for the detection and correction of fading signal conditions in a QAM receiver, resulting in improved information signal recovery.